The goal of this research is to understand the role of immunologically triggered injury to vascular endothelium, and subsequent ischemia and infarction, in skin allograft rejection and in immune rejection of solid tumors. The role of endothelial necrosis and graft infarction will be evaluated morphologically, using 1 micrometer sections and electron microscopy, in epidermal as opposed to full-thickness skin grafts, and in mouse skin grafts containing xeno-\or allogeneic epidermis but syngeneic endothelium. The mechanism of allograft immunity will also be studied by analyzing the pathogenesis of skin lesions produced in an antigen-specific, H-2-restricted fashion by adoptively transferred cloned Lyt-1-2+ cytolytic T\lymphocytes. Long-term clones of strain two guinea pig aortic endothelial and smooth muscle cells will be used to define the nature of T\cell-dependent cytotoxic mechanisms responsible for blood vessel damage in the vicinity of syngeneic line 1 and line 10 guinea pig hepatomas.